AlGaInP-based light-emitting diode is a semiconductor device that converts electrical energy which is injected therein to light having a certain wavelength in the range of 570-630 nm. The wavelength of light that is generated by the light-emitting diode is determined by the magnitude of the band gap of the light-emitting diode. Specifically, the band gap size can be easily controlled by changing the composition ratio of Al to Ga, and for example, as the composition ratio of Al to Ga increases, the wavelength decreases.
AlGaInP-based light-emitting diodes are generally fabricated using a metal organic chemical vapor deposition (MOVCD) system that enables the growth of high-quality layers. Such AlGaInP-based light-emitting diodes generally have a structure in which an AlGaInP-based high-efficiency active layer configured to emit light having a certain wavelength is present between an n-type AlGaInP material layer and a p-type AlGaInP material layer. Because the active layer, the n-type layer and the p-type layer have relatively high resistances, each of the layers is grown to a thickness of 1 μm or less (total thickness: <3 μm) so that the light-emitting diodes will be used for general purposes.
Because the optical efficiency of such AlGaInP-based light-emitting diodes is determined by the internal quantum efficiency and light extraction efficiency thereof, it is required to increase at least one of such determination factors in order to increase the optical efficiency of the light-emitting diodes. An increase in the internal quantum efficiency is generally achieved by enlarging the emission region of the active layer. For this, an active layer having a multilayer structure, a current diffusion layer, and a layer for preventing the overflow of electrons and holes, etc., are mainly used. An increase in the light extraction efficiency is achieved by allowing light emitted from the active layer to be easily emitted to the outside of the light-emitting diode. For this, a reflective layer, a photonic crystal, and surface texturing, etc., are mainly used.
Among the above-described methods, the surface texturing is most widely used in various manners to increase the light extraction efficiency. Particularly, in the case of AlGaInP-based light-emitting diodes, the surface of a GaP layer that is used as an upper current diffusion layer is generally treated by a chemical etching process using a phosphoric acid-based compound to make the surface rough (texturing), thereby forming a light scattering surface. However, the chemical etching process causes defects or contaminants on the GaP surface to thereby deteriorate the characteristics of the AlGaInP-based light-emitting diode. Accordingly, there is a need for a method capable of texturing surfaces without using a chemical etching process in order to increase light extraction efficiency.